Why Does Your Arm Hurt After You Get a Flu Shot?

Pornpak Khunatorn/iStock via Getty Images
Pornpak Khunatorn/iStock via Getty Images

If you’ve ever gotten a flu shot, you may have felt soreness in your upper arm for a day or two afterward. That’s just a sign the vaccine is working, immunologists say.

The flu vaccine works by introducing your body to a foreign substance called an antigen (in this case, the antigen is a deactivated or “dead” virus similar to the flu virus). Being exposed to an antigen “primes” immune system cells, preparing them to create antibodies should they ever encounter the foreign substance again [PDF]. The inactive virus in the vaccine can’t make you sick, but it does help sensitize your immune system to potential threats. Essentially, the vaccine puts your body on high alert for anything resembling the flu virus, enabling you to fight off infections and illnesses faster and more effectively than you could otherwise.

In the process of battling the inactive flu virus introduced by the flu vaccine, your immune system also releases mediators like histamine, which causes inflammation. In the event of infection, inflammation is important because it helps your body fight invaders and repair damaged tissue. But it’s also what causes soreness. The flu shot is usually injected into your upper arm, which is why the early immune response—and any pain—tends to be localized there.

Roughly one in five people have this type of painful reaction, immunologist Richard Zimmerman told Popular Science. If you’re susceptible to soreness after receiving a flu shot, there are a few steps you can take to alleviate the pain. Dr. Juanita Mora of the American Lung Association recommends taking an ibuprofen about two hours before getting the shot.

“You can also try icing the injection site to reduce redness and swelling,” Dr. Mora said.

It’s also important to move your arm around after receiving the shot so the vaccine isn’t quite so concentrated in one place. Barring that, you could always try getting the vaccine in your non-dominant arm so that any pain won’t interfere with your everyday activities.

Any pain is worth it, though: Even if you’ve never gotten the flu before, there’s always a chance you could get it in the future. And getting a flu shot also contributes to herd immunity, helping protect higher-risk populations (like children, older adults, and chronically ill individuals) who often can’t receive the flu vaccine for themselves. Keeping up-to-date on vaccines is one of the easiest ways individuals can contribute to community health.

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Why Are Shower Doors in Hotel Rooms Getting Smaller?

sl-f/iStock via Getty Images
sl-f/iStock via Getty Images

Shower doors are shrinking in posh hotels, and minimalism is to blame, Condé Nast Traveler reports.

In lieu of hanging shower curtains or providing full shower doors, many newer hotels are opting for glass panels that cover only half the length of the shower. That’s frustrating for many travelers, who complain the growing trend is inconvenient and leaves bathroom floors sopping wet and slippery after shower use.

According to Condé Nast Traveler, the half-door trend began in European hotels in the 1980s. “A lot of it comes down to people trying to design hotel rooms with limited space,” boutique hotel designer Tom Parker told the magazine. “It’s about the swing of the shower door, because it has to open outward for safety reasons, like [if] someone falls in the shower. You have to figure out where the door swing’s going to go, make sure it’s not [hitting] the main door. It’s just about clearances.” A smaller door also has the added benefit of making the space appear larger than it really is, according to the magazine.

The trend is also connected to the birth of minimalist “lifestyle hotels,” which cater to a younger, hipper clientele that gravitates toward sleek lines and modern design. Plus, half-size glass doors are easier to clean than shower curtains, which tend to trap bacteria and need to regularly be replaced, which can add up to significant additional costs for a hotel.

Theoretically, even half-door showers are designed to minimize water spillage. Designers try to level the floors in bathrooms so water doesn’t pool in random areas, and they place shower heads and knobs in areas that are more protected by glass paneling. And where design doesn’t work, hotels try to pick up the slack.

“Hotels tend to mitigate the risks by offering non-slip interior shower mats, cloth bath mats for stepping out of the shower, grab bars, [and] open showers or no-sill showers which avoid having to step up and over the ledge,” designer Douglas DeBoer, founder and CEO of Rebel Design Group, told Condé Nast Traveler.

But the half-door trend still has yet to gain much love from hotel guests. “The older generation much, much prefers having a shower door,” Parker told Condé Nast Traveler. “I’m like a 70-year-old man at heart anyway. I like [a shower door] if it’s in keeping with the style of the rest of the room.”

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Does Pushing the Button at a Crosswalk Actually Do Anything?

Pressing this crosswalk button may or may not do something.
Pressing this crosswalk button may or may not do something.
David Tran/iStock via Getty Images

Since crosswalk signals rarely seem to give you the green light (or more accurately, the white, human-shaped light) right after you press the button, you may find yourself wondering if those buttons actually work. The potentially exasperating answer is this: It depends.

First and foremost, it’s important to understand that crosswalk buttons aren’t designed to have an immediate effect; they’re just supposed to tell the system that a person is waiting to cross. As CityLab explained, some systems won’t ever give pedestrians the crossing signal unless someone has pressed the button, while others are programmed to shorten the wait time for walkers when the button has been pressed. No matter what, the system still has to cycle through its other phases to give cars enough time to pass through the intersection, so you’ll probably still have to stand there for a moment.

During busy traffic times or under other extenuating circumstances, however, cities can switch the system to what’s known as “recall mode,” when pedestrian crossings are part of the cycle already and pressing the button quite literally changes nothing. Unfortunately, there’s no way to tell if a particular button is in recall mode, short of calling your city officials and asking an expert to come inspect it.

But if you feel like a button isn’t doing anything, there’s a pretty good chance it’s been permanently deactivated. As congestion has increased and the systems to manage it have become more advanced over the years, cities have moved away from using crosswalk buttons at all. In 2018, for example, CNN reported that only around 100 of New York City’s 1000 buttons were still functioning. Since actually removing the buttons from crosswalks would be a costly endeavor, cities have opted to leave them intact, just waiting to be pummeled by impatient pedestrians who don’t know any better.

What about 'close door' buttons on elevators, you ask? That depends, too.

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